For some survivors and victims' relatives, the attack still echoes as a warning that was unheeded

Volunteer fire warden Alan Fromm rushed into 5 World Trade Center to evacuate his office building; after the South Tower collapsed, he was found unconscious under an ambulance

Church and performing arts center near completion, but one tower expected to take another five years, and construction on another tower won't start until an anchor tenant found

A congressional bill fast-tracking legal status for an estimated 1,000-2,000 people has stalled; 20 years on, only several dozen still protesting

The old St. Nicholas Greek Orthodox Church, which was crushed underneath the falling south tower, is the only house of worship destroyed in the attacks

A look at some of the people who came to the fore in wake of world-altering attacks, and what they've been up to since

Street scenes chart escalating horror as people stare and weep at burning skyscrapers, then run from billowing dust cloud after one of them crumbles

'We made a promise to the families of World Trade Center victims to do whatever it takes for as long as it takes to identify their loved ones,' says top NYC medical official

Guy Sanders, an EMT who was en route when the towers collapsed, killing his colleague, says 'it's not something to be gotten over'

The remembrance this year will likely be different following the recent chaotic US exit from Afghanistan, ending a 20-year war that was sparked by the September 11 attacks